In the prior art, techniques for obtaining information indicating a remaining amount of contents of a container have been developed. For example, patent literature PLT1 discloses a drink refill timing detection system in which, when a container is tilted at an angle larger than a predetermined angle, a refill signal is wirelessly transmitted by movement of a small ball provided to a bottom of the container. Also, patent literature PLT 2 discloses an instruction system which measures a remaining amount of the contents of a container with a remaining amount measuring instrument provided to the container and, when the remaining amount of the contents reaches a predetermined threshold or less, sends information to that effect to a server.